Dealing with stepchildren and their pathetic mothers
I am new to this site, sooo firstly HI EVERYONE 
I would like to know youre thougts on my situation.
Me and my fiance are both divorce, I have one child and he has three. He's been divorced twice, his first wife fell pregnant with their first child when she was only 15yrs old, they then had a second child, after that got divorced, he re-married and had one child with the second wife, he said that happend because he was young and stupid. The 2 children he had with his first wife stays with us, I earn a income, so I also support the children, but my problem is I have this anger feeling inside myself with him in the sense that I give him the fault for everything, my feelings about the children staying with us, having to deal with 2 x wifes, because the mother doesnt contribute nothing whatsoever to her children, I do it all, that also makes me angry because they are pathetic, all of it is all of a sudden my responsibility, I mean I really really want to have another child, but it feels there isnt any space for more, which means my daughter wont have a blood relative, as they have done all the work already, I have one and now have 4 without doing anything. I find it difficult to forget his past and to move on, I will always compare myself to them.
My relationship with the children arent that good either, because I also feel it's their fault, I know it isnt, because if I see them I see their mothers and for that reason I cant stand them, because I truely hate both the b*ches. The child that doesnt stay with us, visit us every school holiday, I cant stand it or her either, I hate it so so very much when she comes to our house, it feels like she is stealing me and my partners time together and all she do is wine, she is the same age as my daughter but would think she is 2years younger.
Does anyone feel the same or am I simply going insane?
So if I understand it right -
So if I understand it right - you are SM to 3 SKIDS - 2 of whom live with you all the time, and one for the holidays - and you work and also have your own child? You do not give the ages of the children but I imagine fairly young.
I am not surprised you feel there is no space for you to have a child with your fiance, and that you feel over-burdened with responsibility - of course you are not going insane - just pulled in all directions.
If you are angry with your fiance because he is not giving you enough support - that would be completely reasonable too.
If it were me in the situation, I would be considering whether I wanted to take the next step of marriage with this man if I am feeling so angry and pressured. I suppose it depends what positive things you get out of the relationship - are they enough to balance the negative?
its ok to admit that maybe
its ok to admit that maybe getting involved with someone who has kids was not for you..especially if your going to give up your chance to have another child of your own. his kids are there for life..and it's not healthy for you or the kids to "mash" this all together if you can't overlook the bio mom's...unfortunately, good mom's or not..those kids love them just as much as they love thier dad and shouldn't feel anything but support in regards to having a relationship 100% with both parents..:(...i have 4 SK and 2of my own. I know how you feel..i would love another child..but i decided it was ok for me to give that up to be with my husband and love and respect his kids as if they were my own. that's not to say that sometimes i don't feel a bit hurt or "empty" in regards to not having another..but i am ok with it..it sits well with me..but if it doesn't for you..don't feel the least bit selfish if you choose to pursue that without him..make yourself happy first and then and only then can you be anything else to someone else